Mini-Duct High Velocity HVAC
Modest scale Utilihab buildings may often rely on passive ventilation with the use of openable windows and soffit vents to the above-ceiling space and discrete room heating and cooling. But for larger structures and less-than-mild climates an active ventilation system linked to a central cooling and/or heating system may be preferred. For this Utilihab favors the use of a Mini-Duct Compact High Velocity HVAC system employing positive pressure ventilation. Conventional central heating and cooling systems rely on large size ductwork which is cumbersome to install or adapt and difficult to integrate into Utilihab’s more minimalist structural system. However, the high velocity ‘mini-duct’ system employ a compact 5mm(2”) ductwork with continuous tubing and a distribution layout that largely parallels the organization common to the Utilihab Modular Wiring and Modular Water Supply systems. A central air handler unit is integrated to cooling or heating modules and feeds a primary ‘plenum’ duct network which then links to the individual mini-duct tubing and registers. Zone dampers in the above-ceiling space allow for moderation of air flow in different rooms or areas of a structure to compensate for solar gain or other local thermal fluctuations so as to improve energy efficiency. In the Utilihab kits for this type of system the return air intake is located near an outside wall with HEPA filtration and Heat Recovery Ventilator modules and thus creates a positive pressure system that is constantly forcing stale air and indoor pollutants out of the structure while recovering some of the heat otherwise exhausted with it for high energy efficiency. Due to increased concern about indoor pollution, positive pressure ventilation is becoming standard in commercial buildings and the use of high-velocity mini-duct systems offers the added health benefit of eliminating dust and mold build-up in ductwork. Utilihab also allows the use of inner channel spaces in larger Primary framing as plenums for air distribution, with special modular fittings allowing for direct attachment of distributor duct tubes and zonal dampeners to these modified ceiling-level beams. This allows for an extremely compact system installation that integrates tightly with the architectural design. However, independent plenum ducts may offer more adaptability in some design situations. The Utilihab Mini-Duct High Velocity HVAC system is typically employed in combined heating, cooling, and ventilation system and may employ either or both floor and ceiling output ducts. But the system can also be used as dedicated heating, cooling, or ventilation in combination with other systems. The Utilihab Mini-Duct HVAC kits consist of the following components; Air Handler Units: a box-like modular fan unit with optional hydronic or electric heater and cooler coil units, HEPA filter unit, Heat Recovery Ventilator unit, and humidifier/dehumidifier units. It can be mounted in vertical or horizontal positions. Often used as individual units for a whole modest sized building, can be used in multiples for large structures. HVAC Management Unit: a microcontroller unit integrated to a series of pressure, air flow, temperature, CO2, and humidity sensors, a series of remote control and display panels or a HomeWeb home control system, and providing control to Air Handler units, boiler and chiller units, humidifier/dehumidifier units, zonal dampener units, Heat Recovery Ventilator units. Designed to manage all these elements to maintain a consistent indoor air quality across a multi-zone system with a constant positive indoor air pressure. May also be used to manage solar thermal systems and can be linked to fire/smoke detection units to provide a high indoor pressure boost in the event of fires so as to aid building occupant escape. Boiler Units: electric or gas powered water heaters serving for both hydronic heating and water heating. They are linked to heater coil units in the Air Handler Units. This can be used in a primary or supplementary heating role in combination with other hydronic heat sources, such as solar thermal systems. Utilihab employs the same boiler units for the Mini-Duct HVAC as employed with its hydronic register or radiant floor heating systems. Chiller Units: electric, gas, or solar powered hydronic chillers linked to the cooling coils of Air Handler units. These are also the same as used with the Utilihab Mini-Split AC systems and radiant ceiling cooling or chilled beam systems. Primary Plenum Ducts: a 100-150mm main air distribution duct used as primary ‘trunk’ lines of the air distribution system. These insulated pipes will usually be routed above ceiling and below floor and within wall volumes. They can use framing pass-through holes with the larger Primary framing types but must usually route around Primary framing. In smaller structures the smaller distribution tubing will be used for most routing while the Primary Plenum us used to construct a kind of air manifold in a utility space. Plenum Beams: modified Primary framing profiles used as Primary Plenum Ducts via special channel port adapters. These beams are usually factory fabricated rather than made by the Utilihab builder and may be custom fabricated to suit particular design situations. Distribution Tubing: 50mm diameter tubing used to distribute air from the Primary Plenum Ducts to air outlets mounted in interior ceiling, floor, and wall panels. A typical system will put a few of these in each room. Long distance distribution tubing may be insulated. Air Outlets: small circular or slotted ports that are mounted in standard Utilihab interior panels, most commonly floor and ceiling. Made of simple single pieces of plastic, these can be custom fitted to most any panel but more common standard panels may also be pre-fitted with them. Zonal Dampener Units: mounted to the Primary Plenum Ducts, these air flow regulators are pulse wave modulation actuated and linked to the Air Quality Management Controller.